// 数学工具
pub mod secr{
    use super::ss::ssr;

    pub fn sum_multi(x:i32, y:i32) -> i32{
        (x+y)*(x+y)
    }

    pub fn sum(x:i32, y:i32)-> i32{
        ssr();
        super::sum(x, y)
    }
}
mod ss{
    pub fn ssr(){
        println!("ssr invoked.")
    }
}
pub fn sum(x: i32, y: i32)-> i32{
    x + y
}
pub fn multi(x: i32, y: i32)-> i32{
    x * y
}
pub fn pow(x: i32, y: i32) -> i32{
    if y == 1{
        return x;
    }
    x * pow(x, y-1)
}
pub fn sum_multi_br(x: i32, y: i32)-> i32{
    self::secr::sum_multi(x, y)
}